SECT. II 



PHYSIOLOGY 



277 



falling from the plant. In Eanunculus Ficaria the roots of the axillary buds are 

 full of reserve food material, and resemble grains of corn. When the plant dies the 

 bulbils remain on the ground, and have given rise to the fable of showers of grain. 

 Dulbils or gemmae are met with also among the Mosses, Liverworts, and Ferns. The 

 winter buds or hibernacula of many water plants {Hydrocharis, TJtricularia, Lemna, 

 etc.) have a peculiar biological significance. They are formed in the autumn, and 

 sink to the bottom of the water ; in the succeeding spring they rise to the surface 

 and form new plants. 



By vegetative multiplication higher plants can annually give rise to individuals 

 which are strong and capable of flowering and fruiting. The seedlings of such 

 plants, on the other hand, often require to grow for several years before the 

 capacity of sexual reproduction is attained (bulbous plants. Hop, etc.). 



In addition to the instances just cited, in which the vegetative reproductive 

 bodies take their origin from points where lateral shoots are normally formed, they 

 may also appear in places where no shoots are normally developed. Thus the 

 adventitious formations often found on leaves, particularly on the leaf-blades, serve 



Fig. 21S — AspUnmm Fahianum. A young plant (T), with leaves and roots {W), has 

 sprung from the leaf (Mj of the older plant. 



the purpose of reproduction. Just as the leaves of Begonia, Drosera, etc. , after 

 they have been cut oft", are able to give rise to new plants, in other cases the leaves 

 possess this power while still growing on the parent plant. Some ferns afford 

 specially characteristic examples of this {Asplenium decvssatum, A. Fabianum, A. 

 bulbifcrum,A. viviparum) ; adventitious buds are jiroduced on their laminae, develop- 

 ing into small rooted plants (Fig. 218). The adventitious buds of Cijstoptcris 

 bulbifera take the form of bulbils with small swollen leaves. Adventitious plant- 

 lets are frequently formed also on the\ea,ves o? Cardamine 2')ratensis, and Cardamine 

 amara manifests a similar tendency. One of the best-known examples of such 

 adventitious formations is afforded by the leaves of the tropical Bryophylhim, in 

 the marginal indentations of which the brood plantlets develop when the leaf is 

 separated from the plant or wounded. Gemmae are abundantly produced on tlie 

 thallus of many Hepaticae {Marchantia, Lunularia), and by their continuous 

 growth the gemma cups (Figs. 371, 372) are always kept well filled. 



Vegetative Multiplication by Single Cells (Spores). — As in the 

 case of multicellular vegetative bodies, multiplication can be eftected 

 also through the separatior of single cells. Strictly speaking, this 

 manner of multiplication actually takes place whenever a division of 



